Weather Terms Explained

This
page offers a description of the different types of warnings, watches,
advisories and statements that may be issued. One of the most important
distinctions to make is the one between
a Watch and a Warning.

Watch
Indicates that conditions are favorable for a particular type of event, but that the event is not
occurring or imminent. Listen to your local media, or keep an eye on
this website, for statements and possible warnings. Watches are intended
to heighten public awareness and should not be confused with warnings.

Warning
A warning means that a particular event is occurring or imminent.Measures should be taken to safeguard life and property.

Non-Precipitation Weather Events

High Wind Watches and Warnings
For a High Wind event, one or both of the following must occur:
1) sustained wind speeds of 40 MPH or greater lasting for 1- hour or longer
2) winds of 58 MPH or greater for any duration

Wind Advisories
A Wind Advisory may be issued for one or both of the following conditions:
1) sustained winds of 31-39 MPH for a period of 1 hour or longer
2) gusts in the 46 to 57 MPH range for any duration of time

Dense Fog Advisory
Dense Fog Advisories may be issued for visibilities
1/4 mile or below. These Advisories will usually be posted for
widespread events, not small local events such as valley fog in the
summer.

Excessive Heat Advisory
The National Weather Service will issue Excessive
Heat Advisories for events that put the Heat Index above 105 degrees for
a period of 3 hours or longer. Remember the Heat Index is the
combination of temperature and humidity, which gives a value that is
perceived by the human body.

Frost and Freeze Warnings
These warnings are most commonly issued during the
fall months from late September to early November. During this period,
advisories will be issued until the first killing frost or freeze
occurs. Warnings will not be needed again until the following fall
unless during the spring months a late season arctic outbreak threatens
vegetation. Frost Warning- used when temperatures at ground level are
expected to drop low enough to form frost on exposed surfaces. This
would not necessarily be a killing frost. Frost Warnings will
normally be issued when temperatures are forecast to fall into the lower
or mid 30s. Freeze Warning- used to describe conditions when
temperatures at ground level are forecast to drop low enough to cause a
hard freeze. Usually, this would be enough to cause significant damage
to tender vegetation. Freeze warnings will be posted if temperatures
plunge to around 30 degrees F or lower. Remember in these types of
situations the forecaster is issuing for temperatures at ground level.
Since temperature instruments are 5 feet above the ground, frost will
often occur when temperature sensors read 36F. A forecaster may choose
to use the wording "patchy frost" or "chance of frost in low lying
areas" when temperatures are expected in the mid 30's to around 40
degrees F.

Air Stagnation Advisory
If during the summer months
winds are very light at the surface and aloft, with no precipitation for
a long duration of time, pollution may build up enough to issue this
type of advisory.

Severe Weather Watches and Warnings

Severe Thunderstorm and Tornado Watches
These watches will be issued for the potential
of severe thunderstorms or tornadoes. Typically, they are issued for a
particular region for a 6 hour time frame. Severe thunderstorms and/or
tornadoes are possible in and close to the watch area during that time
period. It is important to remember that watches do not indicate
immediate danger...but the sky should be watched very closely. Watch or
listen to the local media for future statements and possible warnings.

Flash Flood or Flood Watch
These are issued to indicate thepotential
of flooding or flash flooding over a particular area. Again, there is no
immediate danger, but keep an eye on the water, and be sure to listen
for possible warnings. A flood watch will be issued for situations
related to widespread general flooding. These are generally less
changeable but longer term flooding situations. Flash Flood Watch- will
be issued for situations relating to short term, intense flooding of
small streams and creeks. These situations can be particularly dangerous
and safeguards to life and property should be completed without delay.

Note: The following events are short term life threatening events. Immediate action should be taken upon issuance.

Tornado Warning

Any of the following may require the issuance of a Tornado Warning.
1. Tornado on the ground
2. Funnel Cloud
3. Rotating Wall Cloud
4. Doppler Indicated Tornado - In this case the
Doppler Radar shows rotation in a storm, in which the radar operator may
issue a warning